Research on Recycle and Closed-Cycle Diesel Engines for Underwater Applications

RESEARCH ON RECYCLE AND CLOSEDCYCLE DIESEL ENGINES which can operate where air is not freely available was started and carried out with great enthusiasm in Japan and elsewhere in the world before and during World War II The common objective was the development of prime movers for use in fleet submarines However marked progress in nuclear technology after the termination of the war led to the successful development of nuclearpowered submarines and put a temporary end to research endeavors on recycle and closedcycle diesel engines before they could reach the operational stage In recent years interest in oceanological research and development has grown on an international scale In Japan large rail and sea construction projects have been pushed energetically for the further development of the country These have given rise to an increasing demand for independent power plants which can operate underwater or underground with no requirements for power transmission cables and support vessels or bases Thus recycle and closedcycle diesel engine power plants have once again come into the focus of attention as prospective power sources to fill in the gap that currently exists between lead batteries and nuclear power 123 We have evaluated the prospects of these engines and have been engaged since in 1967 in the basic investigations and development of these engines which could fulfill applications as prime movers in the underwater power plants Mainly here are reported these engines performances from the results obtained through theoretical and experimental investigations and also reported the underwater practical power source HIRUP30 with the hydraulic out put of 22 PS First several technological problems pertaining to the recycle and closedcycle diesel engines but different from the problems of general air environment operation engines were extracted and the expected engine cycles were discussed from a thermo dynamic viewpoint Then landbased testing equipment for the recycle engine was manufactured for a trial with intention to develop an underwater power source With the equipment experiments were carried out to look into the working and the performance of the engine Furthermore the equipment was modified and made into a closedcycle diesel engine for a trial and experiments were conducted The test results were compared with the results of the thermodynamic analysis and the suitability of the analysis method was evaluated Subsequently on the basis of these data we succeeded in developing underwater practical power source HIRUP Accordingly the recycle diesel engine system has various problems which are nonexistent in the operation of diesel engine in an atmospheric environment These include 1 The composition of the working gas and its influences on engine performance 2 The cooling of exhaust gas 3 The mixing of recycled working gas and oxygen 4 Efficient devices for the volumetric control of the oxygen and working gas A schematic diagram of a closedcycle diesel engine is illustrated in Fig 2 It has the same exhaust gas cooling and oxygen volumetric control systems as the recycle diesel power plant The main difference is that in the closedcycle plant the carbon dioxide generated by combustion is absorbed chemically for operation under the completely enclosed condition Hence such gases as nitrogen argon and helium as well as carbon dioxide and steam can be the main composing elements of the recycle working gas In addition to the four listed above the closedcycle plant has the following problem 5 The effective absorption of carbon dioxide and its control Fig 5 Flow chart of the calculation Fig 6 Composition of circulation working gas by modes of engine operation Fig 7 Nitrogen density and operating characteristics Fig 17 Block diagram of oxygen control system Fig 14 Performance of the exhaust gas cooler at rated engine output for air environment operation Fig 15 Performance of the suction gas heater air environment operation Thus net output Ne of the engine bearing a maximum load is equal to engine output Neni minus the power consumed in driving the pump and the compressor Load characteristics of recycle engine even at 100 output where the same volume of fuel as in the air environment operation at 130 output is supplied Also it is reportedly known that CO2 gas if any would retard the precipitation of carbon other hand exhaust gas temperature gives a small gradient of change compared with the result of the experiment and its absolute value is large The main reason for the small gradient of temperature change is that the combustion properties of oxygen are not considered in respect of change against the change of oxygen density and the effective combustion factor ϕx is regarded as constant Also the temperature of exhaust gases at a high level because suction gas temperature in the experiment is 120 130C which is about 100C higher than 20C pertaining to suction gas temperature of the standard cycle in the theoretical analysis and nevertheless a change of heat transfer loss may be due to the fluctuation of initial temperature suction gas temperature Tu in the cycle is not taken into account Also the reason for high exhaust gas temperature is that working specific heat is constant and that in a combustion process is kept constant and that heat loss in an exhaust process is not taken into consideration while exhaust gas temperature is calculated by use of an expression for adiabatic expansion And yet the values of ϕx are equal to each other between the experiment and the theoretical analysis and this is probably due to the included methanol energy In kept constant regardless of the change of ϕ In order that exhaust gas temperature in the theoretical analysis will agree that obtained from the experiment it will be necessary to introduce fixing factors or least a change in heat in order that such gas temperature fluctuation is shown in the theoretical analysis This matter will be dealt with further in Chapter 4 consumes 5 PS 137 kW more than when it is running in an atmospheric environment Thus by setting the net output at 233 PS 238 kW the values of fuel and oxygen consumption were calculated analysis was made by use of the round marked conditions of operation namely suction gas temperature ts maximum exhaust gas temperature tmax engine revolutions no net engine output Pe and suction gas compositions The results of the analysis are triangle marked in Fig 24 The diesel engine prototype which has an electric output of 16 kW combined an underwater recycle diesel engine and an electric power generator Fig 27 shows the appearance of this engine Fig 28 shows a block diagram of the HIRUP30 and HIRUP30E It is a matrix structure that main apparatus and its characteristics of the HIRUP30E differ from those of the HIRUP30 because of the different coolers The other different point is a method of the coupling and cleaning of exhaust gas A duct shown type cooler is adopted in both of them but in the HIRUP30 seawater and in the HIRUP30E circulating Fresh water cooled indirectly by seawater is utilized respectively The only operational procedure is the switching on and off of the diesel engine the rest being sequential and automatic This underwater power plant is also equipped with safety devices that detect changes in factors including pressure temperature and oxygen densities at various points and operation informs manually and automatically in case of any system surpasses the preset values Now the HIRUP30E was tested on a seabed 100 meters deep supplying electric power in an illumination lamp and motordriven tools in a series of sea operations Fig 29 shows its external appearance The capsule 1232 H x 3150 D x 16 accommodating the diesel engine and the electric generator is placed in the center inside volume 400 liters both tanks 430 x 3400L inside volume 400 liters 150 each are independently compressed oxygen and one bottle and a further tank 3162 x 2044L x 6 inside volume 140 liters These last for 102 hours of continuous operation at a power output of 16 kW The amount of compressed air contained in the bottle is sufficient for starting the engine 40 times under normal conditions Since the crane employed for submerging the power plant to its place of installation had a maximum lifting capacity of 3 tons two tanks each 1286 x 3731L x 9 were attached to the bottle racks to create a combined buoyancy of 428 tons and to reduce the weight of the power plant therefore 5040L x 4568W x 3700H and its weight in the atmosphere approximately 20 tons Illustrated Fig 30 are the load characteristics of the electric generator installed in this power plant at an engine speed of 1800 rpmmin1 and a pressure of 11 at 1108 MPa at the gas compressor outlet equivalent to the water pressure at a depth of 100 meters The performance values recorded at a power output of 16 kW 203 V215A 60 Hz 34 W are as follows fuel consumption η fuel 522 gkWh 384 gkWh oxygen consumption b ε 201 kgkWh 1479 kgkWh suction gas temperature at the cylinder inlet t ε 135C and exhaust gas temperature at the cylinder outlet t x 600C As can be learned from Fig 31 the balance of power output under the abovedescribed conditions are power output of the recyled diesel engine η 37 PS 272 kW power loss attributed to the auxiliary equipment 10 PS 1735 kW power loss caused by electric energy for 5 PS 137 kW and net power output 16 kW Thus 68 percent of the power output of the recycled diesel engine is available as the net power output of HIRUP30E The HIRUP30E had been operated for about 100 hours of operation onland and underwater Also it had been lowered to the seabed at a depth of 100 meters 10 days and operated for 35 hours The under water power plant was essentially designed to assess its capability independently of operation in water During the nine days of testing mentioned above some figures recorded about the support service for the power generator and its operating performance The typical values recorded during the enginestarting procedure of the engine are there was no difficulty starting and stopping the diesel engine repeatedly Balance of power output on HIRUP30E The typical values recorded during the engine starting period on a sea bed 100m deep test