Stirling engine for using exhaust gas


Purpose of developing
In order to use energy effectively, it is necessary that not only heat efficiency improvement of combustion engine but also using energy without being utilized. One of no using energy, exhaust gas is picked up. Generally, exhaust gas is used as steam turbine for recovering by boiler. But it is existed that exhaust gas can not be recovered by boiler. Therefore, to produce power from exhaust gas by using Stirling engine, we consider of using energy effectively.
In this report, we constructed Hybrid system that combined the gasoline engine and Stirling engine for exhaust gas, furthermore, examination was carried out about Stirling engine performance.

Structure and specification of Stirling engine for using exhaust gas

4Expansion side piston
5Compression side piston
6Piston ring

HeaterDouble pipingStainless
Regenerator50 mesh wire netBrass
CoolerShell and tubeBrass

Figure shows Stirling engine designed and made by our laboratory. There specifications are given on table.
The exhaust pipe of gasoline engine is connected the heater of Stirling engine by flexible pipe which covers minimum distance between two engines. The connecting pipe and the heater are protected by insulator against heat radiation.
For the heater of the heat exchanger, double piping design is opted in order to recover the maximum heat capacity of exhaust gas. With this design, working gas of Stirling engine passes inside pipe, while exhaust gas flows outside. The material of tube is used Stainless for inhibiting oxidation.
For the regenerator, its material is brass, can be maximally included 60 sheets of 50 mesh. The cooler is adopted by shell and tube, in order to improve thermal conductivity, tube material is brass. Cooling way is compulsory cooled by water.
As for gasoline engine, a small general purpose 4 cycle engine is used to obtain exhaust gas. Gasoline engine has maximum power 8.5ps.

Performance of Stirling engine for using exhaust gas

Table shows experiment conditions which we carried out until now.

Effect of heat capacity with exhaust gasNon-load:800WA40%load:3.5kW
Effect of regenerator number20,40,60sheets
Effect of buffer pressure1,2,3atm

Effect of heat capacity with exhaust gas
Heat capacity with exhaust gas is calculated by quantity of air in gasoline engine, rate of fuel consumption, exit temperature of exhaust gas. For non-load, heat capacity with exhaust gas is 800W, then gasoline engine speed is 3000rpm, exit temperature of exhaust gas is 650. Similarly, for 40%load, each specifications have 3.5kW, 2000rpm, 600.This heat capacity is calculated from exit temperature to atmosphere temperature.

Effect of regenerator number
We carried out experiment to change regenerator number of wire net, 20, 40, 60sheets.In this experiment, gasoline engine was operated 40%load(3.5kW), Stirling engine was operated under stroke 60mm.

Effect of buffer pressure
We carried out experiment to change buffer pressure, 1, 2, 3atm.In this experiment, gasoline engine was operated 40%load(3.5kW). Stirling engine was operated under stroke of 60mm, regenerator number of 60sheets.

Right figure shows the performance of Stirling engine for effect of buffer pressure. In this figure, maximum shaft power was recorded 91.5W under 320rpm.A number 3% in heat capacity of exhaust gas can be recovered by Stirling engine as effective power. In the future, it is expected that recovery percentage fairly improves if number of Stirling engine can be increased.

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