Customer: Reaction Engines Ltd
This test campaign studied the performance of a heat exchanger with a letterbox-shaped cross section for a single module of the HX3 subsystem of Reaction Engines' SABRE engine. This required AEL to design a custom hot gas heat source, which was capable of providing partially combusted air with variable massflow and temperatures controlled from 700K to well in excess of 1200K. Flow uniformity was key for the performance results, so temperature and velocity uniformity for the hot gas source was verified at atmospheric pressure using a pitot probe on a traverse. The customer's experiment was then bolted onto the hot gas source in a custom housing so that it could be tested at elevated pressure.
The program required two separate air feeds; one for combustion at high equivalence ratio and a second for dilution to the required temperature. A hydrogen gas feed was used for fuel, and a separate nitrogen or helium gas feed was used for the heat exchanger coolant. Each of these required closed loop feedback control of massflow (0.1% accuracy achieved) and the coolant feed additionally required active feedback control of pressure (0.5% accuracy achieved). AEL therefore designed a custom actuated high temperature needle valve system to maintain a fixed back-pressure in the heat exchanger as the coolant heats rapidly from ambient temperature. Cooling water was provided to the housing of the experiment in two separate feeds.
This video shows one of the commissioning tests. In the middle of the combustor outlet is a pitot probe which measures flow velocity and temperature. It is mounted on a traverse which allows it to move across the exit aperture in a precise way. The pitot is parked in the middle until the whole system comes up to temperature, after which it traverses across the aperture talking measurements. These showed that the temperature and velocity were well within the customer's specification.