User:Verkningsgrad

The Hedman Cycle (thermodynamic US 6655327 B1) is a split cycle engine (Orgin of George Brayton from 1872). The engine includes a piston compressor, a tank for stored compressed air, a piston combustion expander, an heat exchanger in the tank. The exhaust heat is changed over to the compressed air in the tank. The combustion is performed in the expander, idealy at constant pressure until the inputting of fuel and air stops and the expansion proceeds adiabatic.

In princip the following steps are included: -Isothermal compression which results in less compression work and "cold" air after compression. -Heat exchange in the tank which starts close to the expander and ends close to the compressor -In the expander the work strokes starts idealy with volume expansion work followed by adiabatic expansion. The input of compressed air to the expander is controlled by a free variable inlet valve which is closed depending of the required torque at different engine speeds.

The ideal work stroke: -At first, during constant pressure (= the pressure in the tank), creates wolume expansion work caused by heat exchange aginst the exhaust gas -Thereafter creates, during continued constant pressure, volume expansion work caused by the energy from the burning of fuel -Finally adiabatic expansion.

A kind of George Brayton / Hedman Cycle is named the Scuderi Engine.

Compression and expansion can occure in one and the same cylinder with compression at one side and expansion at the other side of the piston.

To all who feels motivated: Do calculations and compare to the Otto cycle. Do it without any losses too see the potential in above decribed Braytoncycle.

This article is a copy (translation) from http://sv.wikipedia.org/wiki/Hedmancykel