Small Engines as Bottoming Cycle Steam Expanders for Internal Combustion Engines

Sandra Hounsham

doi:10.1155/2017/1742138

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Small Engines as Bottoming Cycle Steam Expanders for Internal Combustion Engines

Rohitha Weerasinghe

Sandra Hounsham

Journal of Combustion

https://doi.org/10.1155/2017/1742138

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9 pages

Abstract

Heat recovery bottoming cycles for internal combustion engines have opened new avenues for research into small steam expanders (Stobart and Weerasinghe, 2006). Dependable data for small steam expanders will allow us to predict their suitability as bottoming cycle engines and the fuel economy achieved by using them as bottoming cycles. Present paper is based on results of experiments carried out on small scale Wankel and two-stroke reciprocating engines as air expanders and as steam expanders. A test facility developed at Sussex used for measurements is comprised of a torque, power and speed measurements, electronic actuation of valves, synchronized data acquisition of pressure, and temperatures of steam and inside of the engines for steam and internal combustion cycles. Results are presented for four engine modes, namely, reciprocating engine in uniflow steam expansion mode and air expansion mode and rotary Wankel engine in steam expansion mode and air expansion mode. The air tests ...

Key takeaways
AI

Small steam engines can serve effectively as bottoming cycle expanders in internal combustion engines.
Experiments confirm that small engines, particularly Wankel and reciprocating types, can operate efficiently with steam.
The optimum supply pressure for maximum efficiency in steam expansion is approximately 30 bars.
The study establishes a baseline for future research on small steam engine performance and reliability.
Engine simulations will complement experimental data, supporting the development of medium-scale steam engines.

Research Article Small Engines as Bottoming Cycle Steam Expanders for Internal Combustion Engines Rohitha Weerasinghe and Sandra Hounsham Department of Engineering, Design and Mathematics, University of the West of England, Coldharbour Lane, Bristol BS16 1QY, UK Correspondence should be addressed to Rohitha Weerasinghe; sujithrohitha@yahoo.com Received 16 January 2017; Revised 4 April 2017; Accepted 20 April 2017; Published 31 May 2017 Academic Editor: Paul Hellier Copyright © 2017 Rohitha Weerasinghe and Sandra Hounsham. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Heat recovery bottoming cycles for internal combustion engines have opened new avenues for research into small steam expanders (Stobart and Weerasinghe, 2006). Dependable data for small steam expanders will allow us to predict their suitability as bottoming cycle engines and the fuel economy achieved by using them as bottoming cycles. Present paper is based on results of experiments carried out on small scale Wankel and two-stroke reciprocating engines as air expanders and as steam expanders. A test facility developed at Sussex used for measurements is comprised of a torque, power and speed measurements, electronic actuation of valves, synchronized data acquisition of pressure, and temperatures of steam and inside of the engines for steam and internal combustion cycles. Results are presented for four engine modes, namely, reciprocating engine in unifow steam expansion mode and air expansion mode and rotary Wankel engine in steam expansion mode and air expansion mode. Te air tests will provide base data for friction and motoring efects whereas steam tests will tell how efective the engines will be in this mode. Results for power, torque, and - diagrams are compared to determine the change in performance from air expansion mode to steam expansion mode. 1. Introduction and Motivation Finding a suitable bottoming cycle for recovery of low grade heat recovered from an internal combustion engine is based on the temperature range of operation and the expected efciency. Termoelectric heat recovery provides a relatively cleaner less complicated option, but with very low efciency. Steam on the other hand has been proven to work in heat recovery cycles with a decent efciency range. Tomas New- comen’s atmospheric engine, today referred to as the New- comen engine, was the frst practical device that harnessed power of steam to produce mechanical work. James Watt developed it further and steam reciprocating engines have been in use for the last 200 years [1]. Te use of steam engines has diminished in the advent of the internal combustion engine and the electric motor. However, steam engines are still being used in various engineering applications, especially in the power generation industry. Small steam expansion engines are in limited use [2]; this is usually because a steam generating system is also required which makes them uneco- nomical. Tere have been attempts to use steam expanders as primary power plant of an automobile [3]; however the present work is based on steam small engines as bottoming cycle expanders. Tere has not been much research done in this area. Particularly, there are no data available on perfor- mance of these engines. Te work is intended to provide a platform for the development of small steam engines that can be used as bottoming cycle heat expanders. Tere are various options as steam expanders, for example, vane rotors and microturbines. However, reciprocating expanders and Wankel engines are readily available as small engines that can be converted into steam expanders. Te range of the engines in the study has been limited by the size and power that can be mounted on the test apparatus, a table-top dynamometer. Essentially, the rage has been restricted to less than 20 cc cylinder capacity. Te primary parameters of the two engines that have been used in the study are listed in Table 1. 1.1. Te Rankine Cycle. Te steam engine generally operates on the Rankine thermodynamic cycle. Rankine cycles [4] have been widely used in both prime movers and bottoming Hindawi Journal of Combustion Volume 2017, Article ID 1742138, 8 pages https://doi.org/10.1155/2017/1742138

2 Journal of Combustion Table 1: Engine data. Engine Four stroke reciprocating engine Wankel rotary engine Model OS 32 SX OS 49 PI Bore (mm) 19.5 N/A Stroke (mm) 17.5 N/A Capacity (cc) 5.23 4.97 Compression ratio 10 : 1 7 : 1 (approx.) p BDC TDC Swept volume 1 2 3 4 5 4  Condenser pressure  Clearance volume Exhaust port opens Steam cutoﬀ Steam chest pressure Figure 1: Rankine cycle reciprocating expander - diagram. cycle expanders. Te reciprocating Rankine cycle has been used in locomotives, ships, and stationary engines. Rotary expanders, primarily, steam turbines, are used in power generation. Te use of rotary engine has been restricted by the optimum operating range it ofers in comparison to the wide range ofered by the reciprocating engine. Te use of the steam expander used in this study is mainly aimed as a directly coupled engine that can operate in sync with an internal combustion engine. A reciprocating engine ofers similar torques power characteristics to an IC engine. Te other main advantage is the availability of small engines that can be converted into steam expanders. 1.1.1. Rankine Cycle with a Reciprocating Expander. A recip- rocating Rankine cycle shown in Figure 1 is explained by the following steps: (1-2) Admission of steam at steam chest pressure. (2-3) Expansion of steam until the exhaust port is open. (3-4  ) Blow down of the steam to condenser pressure. (4-5) Exhaust of steam until the exhaust port is closed. (5-1) Compression of steam lef in the cylinder. Te work and heat for the cycle can be found done by obtaining the specifc enthalpies ℎ  , where  refers to steps in Figure 1. Te theoretical work by the cycle is given by ℎ 2 –ℎ 3 and the heat supplied is given by ℎ 2 −ℎ 1 . Te efciency is given by = (ℎ 2 −ℎ 3 ) (ℎ 2 −ℎ 1 ) . (1) Te pump work is neglected as it is small compared to the heat in. Reciprocating steam expanders were the most common type of expanders, known for their high torque and simple operation. Tese are mostly used as marine and old locomotive prime movers. Te speed achievable from large steam engines is limited. Unifow and counter-fow arrangements are possible with reciprocating expanders [1]. However, the valve arrangements become more complex with counter-fow arrangement [5]. Reciprocating engines are perceived to be easier to implement than Wankel engines [6]. 1.1.2. Rotary Steam Engines. Steam turbines are efcient devices, but the range of operation is limited, hence not very suitable for automotive applications. Te major attraction of the turbine cycle is the high overall efciency in operation. However the fexibility of operation outweighs the efciency factor and makes the reciprocating Rankine cycle more practical. In addition, the ability to cater to fuctuating torque and velocity conditions of the reciprocating cycle makes it the preferred device for automotive applications. Nevertheless, if the energy developed in a turbine is converted into electricity and used to drive an electric motor it leads to a practical solution for hybrid vehicles [7]. An intermediate solution is the Wankel rotary expander [8]. Wankel engine ofers some advantages of both the turbine cycle and the fexibility of the reciprocating engine [9, 10]. Micro-Wankel engines can be fabricated with improved fabrication technology [11]. Attempts have been made to correctly emulate the operation of the Wankel engine [12], but the current application is using steam as the working fuid without internal combustion. Figure 2 shows the theoretical Rankine cycle and the pressure volume diagram of a Rankine cycle. 1.2. Waste Heat Recovery. Te major attraction of Rankine cycle [13] today is its applicability in the waste heat recovery systems [12]. In power generation, Rankine turbines are driven by steam generated through waste heat recovery. Use of reciprocating engines in waste heat recovery systems is seldom. On the other hand, use of rotary steam engines in small scale applications is not common. Ability of Rankine cycle to operate on low grade heat sources such as steam makes it attractive to employ in a bottoming cycle [14]. Two main types of expanders have been applied in Rankine cycle applications that are of two types: frst one is the velocity type, such as axial turbines and radial-fow turbines; the other is positive displacement type, such as scroll expanders, screw expanders, piston expanders, and rotary vane expanders [15]. Tese expanders feed of a steam reservoir courtesy of heat recovery in a bottoming cycle [16, 17].

Journal of Combustion 3 T W in Q out Q out W out 4 1 2 3 Actual cycle Idealcycle S W in Q in Q in W out 4 1 2 3 Expander pump Condenser Steam accumulator 1 2 3 4 Chest pressure Exhaust pressure p  Figure 2: A simple Rankine cycle and Wankel Rankine expander - diagram. 2. Experimental Setup Te experimental setup consists of a dynamometer, a data acquisition system controlled by LabVIEW sofware, a steam/air supply, and a condenser unit. Te sensor inputs are fed to the system through a multichannel data acquisition card. Figure 3 shows the components of the system and how they are linked. 2.1. Te Dynamometer. Testing of small scale engines ofer the advantages of portability, less instrumentation, low space costs, and fexibility. However there are no readily available dynamometer setups for testing small engines. Hence, a small scale dynamometer facility pictured in Figure 4 had to be developed to mount the small engines for testing. Te dynamometer was derived from a model makers’ lathe and the drive train was modifed to absorb power and to motor when necessary. Te engine output shaf is mounted inline with the lathe shaf. Torque transducer arrangement connects the engine output shaf and the lathe shaf. A 400 W DC motor drives the main shaf that can also absorb power. Te end of the drive shaf is ftted to a pulse encoder that generates three pulse streams, namely, (i) pulse per revolution (ppr), (ii) pulse per revolution −90 ∘ (directional indicator), and (iii) pulse per crank angle degree (pcd). Te engines used were modifed model hobby engines manufactured by OS (Japan). Te following data are available of the engines used. For the use as steam expanders, the inlets and exhausts had to be modifed to induct and exhaust steam. Te engine heads were modifed to accommodate for steam connections. Figure 4 shows a schematic of how the steam induction and exhaust connections and valves are confgured. Te picture shows the confguration of the ports controls and steam in and out. Te arrangement is the same for the rotary engine except for the fact that the rotary engine has two inlet valves and two exhaust valves. Te opening and closing of the rotary engine valves take place without electronic control. 2.2. Steam Expanders. Steam expanders are available in the form of reciprocating expanders and rotary expanders. In the Control soﬅware (LabVIEW) Computer Motor controller Data acquisition card (NI) Temperature and pressure sensors Optical encoder Torque transducer Steam Engine Reheater Motor Condenser Scale Figure 3: Te experimental setup. present context unifow reciprocating expander and a rotary Wankel engine are tested. 2.2.1. Reciprocating Steam Engine. A two-stroke internal combustion engine has been modifed to accommodate steam admission through an electrically operated overhead valve. An automotive fuel injection valve has been modifed for the purpose. Te steam enters through an electrically

4 Journal of Combustion Inlet valve Exhaust valve Pressure transducer Temperature sensor Steam quality measurement Steam quality measurement Steam generation Control Control Figure 4: Schematic of the cylinder arrangement. operated inlet valve and exhausts through a port at the BDC. Te timing of steam admission is critical for propulsion. Te valve timing was set to 3 ∘ BTDC and kept for 100 ∘ for the inlet valve. Exhaust takes place through a 6 mm long 25 mm wide port before BDC. 2.2.2. Valve Arrangement for the Two-Stroke Reciprocating Engine. Two pulse streams are utilized from the optical encoder by the data acquisition card, the pulse per revolution (ppr), and the pulse per crank angle degree (pcd). Te ppr pulse is aligned with the top dead centre of the piston. LabVIEW sofware that controls the actuation of the valve and samples the data for storage uses the pcd pulse as a source of clock ticks and ppr pulse as a trigger for an output pulse. Te timing of the valve actuation is synchronized with pcd pulse and is variable. 2.2.3. Wankel Steam Engine. A modifed small scale internal combustion Wankel engine is used as a steam expander. Te fow through the Wankel engine is unifow, and continuous generation of torque is available with three expansions per cycle of the rotor. Te -V diagram for a Wankel Rankine cycle is not available in the literature. However, Figure 9 shows a pressure plot drawn against the crank angle as that is more appropriate than a -V diagram. A 5 cm 3 model Wankel engine has been modifed to run as a Wankel steam expander. Tere are two inlet ports and two exhaust ports. Tey were changed to obtain optimum performance. Te inlet port is at 20 ∘ to the original line of the engine and the exhaust valves have been changed to a side exhaust arrangement as in Figure 5. 2.3. Instrumentation and Measurements. Te engine is sup- plied with air or steam as appropriate and the fuid fow rate is controlled electronically. Measurements were taken at two set pressures of 7 bars and 15 bars for air and steam, respectively. Pressure, temperature, torque, speed, and pulse signals are fed through the National Instruments (NI) data acquisition card to the computer. Communication with the scales takes place via an RS232 connection. All the data acquisition and control are performed using LabVIEW sofware. Te sampling was triggered by the pulse per crank angle degree (pcd) pulse from the optical encoder. Steam in Torque meter Injector To main shaﬅ Steam Engine T P Figure 5: Te dynamometer with the reciprocating engine mounted;  = pressure sensor;  = thermocouple. 2.3.1. Pressure. Pressure measurements were acquired for the engine inlet, engine outlet, inside of the cylinder, reheater inlet, and reheater outlet via piezoelectric pressure sensors. 2.3.2. Temperature. Te temperatures at engine inlet, engine outlet, inside of the engine, reheater inlet, and reheater outlet were acquired using  type thermocouples. 2.3.3. Torque and Speed. Torque and speed are obtained via the inline torque transducer, from these readings power is given by  = 2. (2) 2.3.4. Mass Flow Rate. Te condensate from the engine is collected in a vessel on the electronic scales. Te incremental weight against time gives the mass fow rate. 2.3.5. Steam Quality. Te analysis of the steam quality of the exhausted steam required a new device setup. Te steam coming out of the engine is wet and hence, the pressure and temperature alone would not give the steam condition. A reheater section is ftted to the exhaust pipes which brings the steam to a superheated condition at which the pressure and temperature alone would be able to give the state of the steam. Figure 6 shows the temperature and pressure tapping point and Figure 7 shows the steam quality analyzer. Pressure and temperature sensors are placed at the input to the SQA (ri) and the exit point from the SQA (re). Te readings are used to obtain the specifc enthalpy ℎ re at re from steam tables. Ten, ℎ ri is given by ℎ re −ℎ ri =   , (3) where  is the mass of water collected in time t. VI is the recorded voltage and current used by the reheater section. Te most important measurements of the system are the pressures and temperatures of the inlet, outlet, and inside of

Journal of Combustion 5 Steam in Engine casing T P T Coupling to main shaﬅ Steam out Figure 6: Te Wankel engine;  = pressure sensor;  = thermocou- ple. Δe = VIt p re p ri T re T ri ri re T s Figure 7: Steam quality analyzer (SQA). the engine. Tese measurements can be used to determine the inlet and outlet conditions of the steam and hence to develop an energy balance. 2.3.6. Engine Efciency. Efciency of the engine can be calculated with the heat input values and the power developed by the engine. 3. Engine Test Results Figures 10 and 13 show the power curves for diferent inlet pressures of the engine. Te optimum supply pressure lies around 30 bars that has been confrmed by previous Prasad [7]. Pressures above this range will have a negative efect which is explained by a close analysis of the Molier diagram for water. Saturated steam at pressures above 30 bars stores less enthalpy than steam at 30 bars. Peak to peak measurements of pressures have been taken and the data are referred against supply pressure of zero. Te readings are Crank angle versus pressure per speed step 3 4 5 6 7 8 9 10 Pressure (bar) 50 100 150 200 250 300 350 0 Crank angle 100 rpm 100 rpm 2300 rpm 2300 rpm Wankel engine 7-bar air tests Figure 8: Wankel engine 7-bar air tests, crank angle versus pressure. P-v diagram per speed step 2300 rpm 100 rpm 3 4 5 6 7 8 9 10 Pressure (bar) 2 3 4 5 1 Volume (meters cubed) ×10 −6 Wankel engine 70-bar air tests Figure 9: Wankel engine 7-bar air tests, - diagram. plotted afer taking the ofset into account and refect the absolute value. 3.1. Air Tests on Wankel Engine. Air test data was acquired for rpm values 100, 200, 300, 500, 700, 900, 1100, 1300, 1500, 1700, 2000, and 2300. Te pressure volume diagram for air tests for the Wankel engine is given in Figure 9 for 7-bar air. Te pressure-crank angle relationship is shown in Figure 8. When the supply pressure is low, substantial motoring takes place and is illustrated by the negative pressures in the -V diagram. Air test data was acquired for rpm values 200, 300, 500, 900, 1300, and 1700. 3.2. Steam Tests on Wankel Engine. Steam tests were done at 10-bar supply pressure and 15-bar supply pressure. 15-bar results are shown here as 15 bars was the highest pressure

6 Journal of Combustion Speed versus power and torque Power Torque Speed (rpm) 2500 2000 1500 1000 500 0 0 10 20 30 40 Power (W) 0 0.2 0.4 0.6 0.8 Torque (Nm) Wankel engine 7-bar air test Figure 10: Wankel engine power and torque for 7-bar air. Crank angle versus pressure per speed step 200 rpm 200 rpm 1700 rpm 1700 rpm 6 8 10 12 14 16 18 20 Pressure (bar) 50 100 150 200 250 300 350 0 Crank angle Wankel engine 15-bar steam tests Figure 11: Wankel engine 15-bar steam tests, crank angle versus pressure. at which data were logged as in Figures 11 and 12. Tests were done with a pressure regulated steam supply of an industrial boiler. Te major observation expected of the pressure characteristics of the steam tests is the efect of expansion. 3.3. Air and Steam Tests on Reciprocating Engine. Measure- ments were taken on the expansion of steam at 10 bars in the reciprocating engine. Data was obtained only at 200 rpm to 800 rpm. Tis is deemed appropriate as the engine is expected to run at a lower speed than the IC engine. Te shape of the -V diagram is signifcantly consistent with the theoretical P-v diagram per speed step 1 1.5 2 2.5 3 3.5 4 5 4.5 Volume (meters cubed) ×10 −6 4 5 6 7 8 9 10 11 12 13 14 Pressure (bar) 200 rpm 200 rpm Wankel engine 10-bar air tests Figure 12: Wankel engine 15-bar steam tests, - diagram. ×10 4 3 3.5 4 4.5 5 5.5 6 Speciﬁc power (watts) 0 2 4 6 8 10 12 Torque (Nm) 400 600 800 1000 1200 1400 1600 1800 2000 2200 200 Speed (rpm) Power at 10 Power at 15 bars Torq at 10 bars Torq at 15 bars bars Figure 13: Te Wankel engine power and torque for 10-bar and 15- bar steam. diagram as shown in Figure 14. Specifc power and torque characteristics are shown in Figure 15 at 10 bar. Te power torque diagram is also pretty impressive and is of expected shape except for the readings at 400 rpm. However, the general behavior is as expected. Table 2 summarizes the results obtained for the air and steam tests. Air test diagrams are not shown in here as they were done only for validation purposes. 3.4. Analysis of Results. Te - diagrams for air and steam expansion in rotary and unifow reciprocating engines are presented. Te - characteristics of the Wankel expander

Journal of Combustion 7 × 4 1 2 3 4 0 0 4 8 12 200 p 3 r m 00 p 5 r 00 Volume (m 3 ) Figure 14: -V diagram, reciprocating engine, 10-bar steam, with solenoid inlet valve. 0 0.1 0.2 0.3 0.4 0.5 Torque (Nm) 0 500 1000 1500 2000 2500 Speciﬁc power (watts) 250 300 350 400 450 500 550 600 200 Speed (rpm) Power at 10 bars Torq at 10 bars Figure 15: Specifc power and torque, reciprocating engine, 10-bar steam. are shown in Figures 9 and 12. Te pressure against crank angle diagram for the Wankel engine shows a clear expansion of steam at low speeds. Te expansion efect diminishes with higher speeds. Tis is better explained by the torque curve for the same. Te torque developed is high at lower speeds. Te clear reason for this behavior is the time taken by steam to expand [18]. Te expansion of steam is much higher than that of air and the energy release is clearly visible. Te maximum power curve for air gives a maximum at around 1000 rpm Table 2: Performance comparison of the engines. Wankel engine Reciprocating engine Maximum power (air) 1400 W/kg 2800 W/kg Maximum torque (air) 0.80 Nm 0.38 Nm Maximum power (steam) 5550 W/kg 2600 W/kg Maximum torque (steam) 11.65 Nm 0.45 Nm whereas this for steam is at around 400 rpm. Tis shows the higher expansion rate of air. Te steam coming out of the engines being wet means that there is a phase change in the expansion process. Te phase change process is slower than the direct expansion of air. However, when these are used as bottoming cycles it is necessary to have a reduction ratio of around 10 : 1 to run parallel with an internal combustion engine. Tis is due to the fact that optimum operating rpm rage of steam expanders lies within 100 to 250 whereas IC engines run optimum around 2000 rpm. Te slow operation of steam does not make it a less favored candidate as a bottoming cycle expansion medium. It allows the steam to build up and consumes at a slower rate as well. Once properly geared this should supply enough boost torque through the drive train. In addition to the results obtained from testing, certain issues were highlighted during testing. Te quality of the steam is critical to the prolonged operation of the engine [19]. A closed cycle system is hence preferred to an open cycle. Te steam admission valve design is critical in the injection of steam into the cylinder. A mechanical device may be more robust, at least for the parts that are in contact with steam. Te small engines may sufer from them being small, so that the endurance of the engines is low. It is anticipated to obtain better endurance from those engines. Proper scaling can be done when all the simulation and test data are available for the engines. 4. Conclusion and Future Work Performance measurements have been carried out to predict the suitability of small engines as steam expanders. Te engines have been modifed to suit steam expansion. Te operating speed range of steam is much lower than that of internal combustion engine. Tis prevents us making direct comparisons. Te air tests provide a much comparable set of data for the expanders. Comparing the maximum power and torque data of the two engines it is evident that the Wankel engine provides a much better device as an expander. Te major aim of this work is to measure the suitability of Rankine steam cycle as a heat recovery bottoming cycle and compare the performance of two engine types, the reciprocating engine and the Wankel engine. Te power and torque characteristics shown for small engines make them very suitable for the purpose. Te work involves the development of complete Rankine bottoming cycle including controls. Tis includes the heat recovery system and thermal control of the IC engine and the steam cycle. Endurance tests need to be done to steam engines developed to check the

8 Journal of Combustion longevity [3, 20]. Separate work is being done to develop the control strategies and techniques. Te scaled down dynamometer developed to measure the performance of the engine provides a very useful tool for scaled model testing. Te torque and power curves obtained could be scaled up for a full size engine. Te valve timing for the two-stroke engine is a sensitive factor in the engine performance. Small engines do not allow a great deal of fexibility for us to change this. Only the timing can be changed with electronic triggering. In a full scale engine, much larger valves can be employed and there will be room for fner adjustment. Te tests revealed a number of areas for improvement. Te reliability of the engines could be a major issue. Use of steam oil that improves reliability is possible with a closed cycle. In an open cycle this becomes an emission issue as it will be released to the atmosphere. Using small engines to determine engine characteristics supplies a basis for designing medium scale steam engines. Te fnding can be backed up by simulations once a complete set of data are available. Te authors intend to do further testing on a larger engine with a heat recovery system attached to an internal combustion engine. 4.1. Engine Simulations. Te results can be compared with results obtained from 1D engine simulation results. Values can be obtained for air expansion and an optimum operating point can be obtained. No simulation results are presented at this moment. Initial comparisons which are not presented here, however, suggest that the measurements can be backed by simulations. Tese results show that steam expanders, even at small scale, are suitable devices for heat recovery bottoming cycles. A full set of simulations as described above can be used for scaling up of the fndings for commercial engine applications. 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When comparing reciprocating and Wankel engines, which is more suitable for heat recovery?add

The results indicate that the Wankel engine shows superior power and torque characteristics as a steam expander, outperforming the reciprocating engine in this specific application.

Small Engines as Bottoming Cycle Steam Expanders for Internal Combustion Engines

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