China
Africa
Explore chapters and articles related to this topic
Subsonic Transport Aircraft
Published in G. Daniel Brewer, Hydrogen Aircraft Technology, 2017
Other important assumptions which were made included the temperature of the liquid hydrogen fuel at the high pressure fuel pump outlet, an average value for the specific heat of hydrogen between the high pressure pump and the combustor, and the temperature of the fuel as it enters the conbustor. The fuel pump outlet temperature of 90°R was calculated based on an assumed temperature rise through fuel system feed lines and the temperature rise across the engine high pressure fuel pump. Over the range of temperatures encountered, the specific heat of LH2 is not constant but can be approximated by a constant of 3.5 Btu/lb/°R. The fuel temperature into the combustor was assumed equal to the temperature out of the last engine heat exchanger for all concepts except the expander cycle. For that concept, it was assumed equal to the temperature out of the hydrogen expansion turbine.
Rocket Engines
Published in Ahmed F. El-Sayed, Aircraft Propulsion and Gas Turbine Engines, 2017
It includes a propellant tank, feeding system, reactor, and a convergent–divergent nozzle. As described in Section 19.6, the feeding system cycles may be (1) a gas generator system, (2) a staged combustion system, or (3) an expander cycle. An expander cycle is shown in Figure 19.28 where liquid propellant is pumped from its tank to the reactor through the shell jacketing the exhaust nozzle. Then it flows upward through the neutron reflector surrounding the reactor core, cooling both the reflector and the control drums contained within it, before passing through a neutron and gamma ray shield placed at the upper end of the reactor assembly to limit the radiation heating of the propellant in the tank. Flowing downward, the propellant cools the reactor support structure and is heated to the design temperature, exiting into the nozzle plenum chamber prior to being discharged through the exhaust nozzle. A small portion of the heated gas (propellant) is bled off from this chamber and is cooled (by mixing the heated material with cold fluids) to an acceptable inlet temperature for the pump drive turbine. The turbine exhaust expands in a small nozzle and provides a small portion of total thrust.
Preliminary Results for In-Situ Alternative Propellants for Nuclear Thermal Propulsion
Published in Nuclear Technology, 2022
Dennis Nikitaev, L. Dale Thomas
The bleed cycle water A-NTP engine also considers boiling inside the reactor and can function only using the hot bleed flow to power the turbines since all flow upstream of the chamber will be liquid.8 The boiling inside the reactor will result in high errors in analytical predictions due to two-phase heat transfer correlations yielding results within 50% to 100% error even in laboratory conditions.19,20 Reliable operation of a rocket engine requires supercritical phase change to discourage boiling.21 The use of the hot bleed flow significantly limits the chamber temperature up to 1150 K according to current turbine material limitations.22–24 Therefore, to produce higher Isp from a water A-NTP engine, an expander cycle must be utilized.