Impact of Release Temperature on Hydrogen Jet Mixing with Ambient Air

Qiang Ge; Zhenbiao Zhou; Daniel Creedon; Yi Yang; Michael J. Brear; Deepak Saini; Joseph D. Berry; Mohsen Talei; Richard D. Sandberg; Melissa Kozul

doi:10.58895/hysafe.79

Impact of Release Temperature on Hydrogen Jet Mixing with Ambient Air

Volume 3 (2026): Issue 1

By: Qiang Ge , Zhenbiao Zhou , Daniel Creedon , Yi Yang , Michael J. Brear , Deepak Saini , Joseph D. Berry , Mohsen Talei , Richard D. Sandberg and Melissa Kozul

Open Access

|Sep 2026

Figures & Tables

Schematic of scalar dissipation in an ideally expanded jet issued from a notional nozzle. Scalar decay can be described by a hyperbolic function along the axial direction and a Gaussian function along the radial direction (Kleinstein, 1964).

Table 1

Release conditions, measurement methods and centreline decay rates of past hydrogen release experiments.

EXPERIMENT	RELEASE TEMPERATURE AND PRESSURE	NOZZLE DIAMETER (MM)	MEASURED PARAMETER (P)	MEASUREMENT METHOD	EFFECTIVE NOZZLE SIZE (D_EFF)	CENTRELINE DECAY RATE (P^–1* VS. Z/D_EFF) (EQUATION (2))
Friedrich et al. (2012)	34–65 K 7–35 bar	0.5, 1	Mass fraction	BOS and thermal couples	$D_{e} \sqrt{\frac{ρ_{r}}{ρ_{a}}}$	0.233
Hecht and Panda (2019)	48–61 K 2–5 bar	1, 1.25	Mass fraction, mixture temperature	Raman scattering	$D_{e} \sqrt{\frac{ρ_{r}}{ρ_{a}}}$	0.277 (mass) 0.0281 (temp)
Hecht and Panda (2019)	48–61 K 2–5 bar	1, 1.25	Mass fraction, mixture temperature	Raman scattering	$D_{e} \sqrt{\frac{ρ_{e}}{ρ_{a}}}$ reanalysis with noise reduction (Li et al., 2023)	0.22 (mass) 0.023 (temp)
Veser et al. (2011)*	35, 80 and 290 K 5–60 bar	1, 2, 4	Velocity, mass fraction	PIV and Sampling probe**	$D_{e} \sqrt{\frac{ρ_{e}}{ρ_{a}}}$	0.193 (velocity) 0.313 (mass)
Ruggles, (2015) and Ruggles and Ekoto (2012)	296 K 10 bar	1.5	Mass fraction	Rayleigh scattering	$D_{e} \sqrt{\frac{ρ_{e}}{ρ_{a}}}$	0.214 (Ruggles, 2015) 0.222 (Ruggles and Ekoto, 2012)
Ruffin, Mouilleau and Chaineaux (1996)*	288 K 40 bar	25	Mass fraction	Pellistor hydrogen sensor	$D_{eq} \sqrt{\frac{ρ_{eq}}{ρ_{a}}}$	0.27

P: measured scalar; P*: normalized scalar, definition in equation (2); D_eq: equivalent diameter (notional nozzle exit); D_e: nozzle diameter; ρ_e: density at the nozzle exit; ρ_eq: equivalent density at notional nozzle exit; ρ_a: ambient air density; ρ_r: storage density.

*Horizontal release.

**Hydrogen analysed offline, sensor type not reported.

Schematic of the hydrogen release facility.

Table 2

Storage conditions for the release temperature test at fixed release pressure.

TEST #	NOMINAL RELEASE PRESSURE (kPa)	p (kPa)	T (K)	D (mm)	D_eff (mm)	JET REYNOLDS NUMBER (Rr)* 10⁵	MEASURED MASS FLOW RATE (g/s)	CALCULATED MASS FLOW RATE (g/s)*
1	300	294	35	1	1.02	4.15	0.43	0.46
4		294	48	1	1.02	2.54	0.36	0.38
7		298	70	1	1.03	1.47	0.29	0.32
12		301	119	1	1.03	0.70	0.21	0.24
17		297	290	1	1.04	0.21	0.13	0.15
6	500	484	69	1	1.13	2.47	0.48	0.52
9		506	103	1	1.14	1.46	0.40	0.44
13		509	126	1	1.15	1.07	0.34	0.39
15		498	289	1	1.18	0.37	0.22	0.25

* The calculated mass flow rate assumes choked flow using the nozzle diameter and upstream temperature and pressure of the nozzle. Same for Table 3.

Table 3

Storage conditions for the release temperature test at fixed mass flow rates.

TEST #	NOMINAL MASS FLOW RATE (G/S)	P (KPA)	T (K)	D (MM)	D_EFF (MM)	JET REYNOLDS NUMBER (RE)* 10⁵)	MEASURED MASS FLOW RATE (G/S)	CALCULATED MASS FLOW RATE (G/S)
7	0.30	298	70	1	1.03	1.47	0.29	0.32
11		409	108	1	1.09	1.08	0.3	0.35
14		627	290	1	1.27	0.50	0.3	0.32
4	0.36	294	48	1	1.02	2.54	0.36	0.38
10		468	105	1	1.12	1.31	0.36	0.4
18		747	290	1	1.35	0.60	0.36	0.38
1	0.43	294	35	1	1.02	4.15	0.43	0.46
8		561	101	1	1.17	1.63	0.44	0.49
16		959	289	1	1.48	0.71	0.43	0.47

Centreline decay at the release temperature of 35–290 K and a fixed release pressure of 300 kPa: **(a)** hydrogen mole fraction, **(b)** mixture temperature, **(c)** hydrogen mass fraction decay correlation and **(d)** normalized mixture enthalpy decay correlation.

Centreline decay at the release temperature of 69–289 K and a fixed release pressure of 500 kPa: **(a)** hydrogen mole fraction, **(b)** mixture temperature, **(c)** hydrogen mass fraction decay correlation and **(d)** normalized mixture enthalpy decay correlation.

(a) Mixture mass-based *C_p* as a function of hydrogen mass fraction and mixture temperature. The lines represent the mixture *C_p* along the centreline for releases at 35–290 K; **(b)** centreline mixture enthalpy (*H_CL*) as a function of mixture temperature for releases at 35–290 K.

Centreline decay at the release temperature of 70–290 K and a fixed mass flow rate of 0.30 g/s: **(a)** hydrogen mole fraction, **(b)** mixture temperature, **(c)** hydrogen mass fraction decay correlation and **(d)** normalized mixture enthalpy decay correlation.

Centreline decay at the release temperature of 48–290 K and a fixed mass flow rate of 0.36 g/s: (a) hydrogen mole fraction, (b) mixture temperature, (c) hydrogen mass fraction decay correlation and (d) normalized mixture enthalpy decay correlation.

Centreline decay at the release temperature of 35–289 K and a fixed mass flow rate of 0.43 g/s: **(a)** hydrogen mole fraction, **(b)** mixture temperature, **(c)** hydrogen mass fraction decay correlation and **(d)** normalized mixture enthalpy decay correlation.

Centreline decay rate of mass fraction and enthalpy as a function of release temperature **(a, b)** and jet Reynolds number **(c, d)**. Experimental data from this work (black circles), cryogenic literature data (blue triangles) (Friedrich *et al.*, 2012; Hecht and Panda, 2019), room temperature literature data (red squares) (Ruggles, 2015; Ruggles and Ekoto, 2012). The dashed line in **(a)** and **(b)** indicates the trend of decay rate for the cryogenic jets measured in this work.

Radial decay of hydrogen mass fraction and mixture enthalpy at different release temperatures and a fixed release pressure of 300 kPa. **(a)** 35 K, **(b)** 48 K, **(c)** 70 K, **(d)** 119 K and **(e)** 297 K; black markers and lines represent normalized mass fraction, and red markers and lines represent normalized mixture enthalpy; different line types signify different downstream locations.

Table 4

Table for all radial decay Gaussian coefficients.

TEST #	RELEASE TEMPERATURE (K)	RELEASE PRESSURE (KPA)	RELEASE MASS FLOW RATE (G/S)	MASS FRACTION η_Y				ENTHALPY DECAY η_Y
				DOWNSTREAM LOCATION OF MEASUREMENTS (MM)
				50	80	90	100	50	80	90	100
Fixed pressure 300 KPa
1	35	294	0.43		59		60		64		60
4	48	294	0.36		62		54		71		79
7	70	298	0.29		61		73		66		90
12	119	301	0.21	35	36			39	42
17	290	297	0.13	31	36			32	39
Fixed pressure 500 KPa
6	69	484	0.48		38		34		38		38
9	103	506	0.40	39	42			40	43
13	126	509	0.34	22	18			23	22
15	289	498	0.22	48	46			50	49
Fixed mass flow rate of 0.30 g/s
7	70	298	0.29		61		73		66		90
11	108	409	0.30		40	42	40		44	50	50
14	290	627	0.30	37	40	37	38	38	41	38	39
Fixed mass flow rate of 0.36 g/s
4	48	294	0.36		62		54		71		79
10	105	468	0.36		44	46	45		49	54	57
18	290	747	0.36	37	38	35	36	38	39	36	37
Fixed mass flow rate of 0.43 g/s
1	35	294	0.43		59		60		64		60
8	101	561	0.44		37	38	35		40	47	42
16	289	959	0.43		44	43	41		46	43	42

Radial decay rate of mass fraction and enthalpy as a function of release temperature **(a, b)** and jet Reynolds number **(c, d)**. Experimental data from this work (black circles), cryogenic literature data (blue triangles) (Hecht and Panda, 2019), room temperature literature data (red squares) (Ruggles, 2015). The dashed line in (a) and (b) indicates the trend of decay rate for the cryogenic jets measured in this work.

*Le_t* as a function of the release temperature, based on **(a)** the ratio of axial decay rates for enthalpy and mass fraction, and **(b)** the ratio of radial decay rates for mass fraction and enthalpy. The *Le_t* fitting for release temperature at 70 K or higher (35 and 50 K neglected and circled in red). Same *Le_t* plotted as a function of jet Reynolds number in **(c)** and **(d)**. Experiment data from this work (black circle), literature data (blue triangle) (Hecht and Panda, 2019).

Table 5

Turbulent Pr_t and Sc_t estimation for release at 103 K, 506 KPa.

PARAMETERS		VALUE
Axial decay rate	Mass fraction κ_y	0.199 (measured)
	Enthalpy κ_h	0.162 (measured)
	Velocity κ_v	0.156 (CFD)
Axial turbulent parameters	${Le}_{t} = \frac{κ_{h}}{κ_{y}}$	0.81 (measured)
	${Pr}_{t} = \frac{κ_{v}}{κ_{h}}$	0.96 (calculated using CFD)
	$S c_{t} = \frac{κ_{v}}{κ_{y}}$	0.78 (calculated using CFD)
Radial decay rate	Mass fraction η_y	40.5 (measured)
	Enthalpy η_h	41.5 (measured)
	Velocity η_v	62 (CFD)
Radial turbulent parameters	${Le}_{t} = \frac{η_{y}}{η_{h}}$	0.96 (measured)
	${Pr}_{t} = \frac{η_{h}}{η_{v}}$	0.67 (calculated using CFD)
	$S c_{t} = \frac{η_{y}}{η_{v}}$	0.65 (calculated using CFD)

Hydrogen mole fraction (%) contour at different release temperatures and a fixed release pressure of 300 KPa: **(a)** 35 K, **(b)** 48 K, **(c)** 70 K, **(d)** 119 K, **(e)** 290 K and **(f)** contours of 20% H₂ mole fraction at different release temperatures.

Hydrogen concentration contour at different release temperatures and a fixed mass flow rate of 0.43 g/s: **(a)** 35 K, **(b)** 101 K, **(c)** 289 K and **(d)** contours of 20% H₂ mole fraction at different release temperatures.

Examination of the applicability of adiabatic mixing to the cryogenic release experiments. *X_{H2,calculated}* is from equation (7). Both axial and radial measurements are plotted; the black line is the linear fitting of all plotted data. A slope of 1 means perfect adiabatic mixing.

Comparison of measured and simulated centreline hydrogen molar fraction and mixture temperature at different release temperatures and a fixed release pressure of 300 kPa: **(a)** 35 K, **(b)** 48 K, **(c)** 70 K, **(d)** 119 K and **(e)** 290 K; symbols for experiment data and curves for HyRAM simulation; black for hydrogen mole fraction and red for mixture temperature.

Comparison of the measured and simulated radial hydrogen mole fraction and mixture temperature at different release temperatures and a fixed release pressure of 300 kPa, **(a)** 35 K, **(b)** 48 K, **(c)** 70 K, **(d)** 119 K and **(e)** 290 K; solid lines are fitted from measurements (markers) and dashed lines represent results from the HyRAM+ 6.0 simulation; black for hydrogen mole fraction and red for mixture temperature.

Articles in this issue

DOI: https://doi.org/10.58895/hysafe.79

Journal RSS Feed

Language: English

Page range: 284 - 304

Submitted on: May 14, 2026

Accepted on: Aug 24, 2026

Published on: Sep 10, 2026

Published by: KIT Scientific Publishing

In partnership with: Paradigm Publishing Services

Keywords:

Cryogenic hydrogen release,

Turbulent jet mixing,

Decay rate,

Turbulent Lewis number,

Liquid hydrogen safety

© 2026 Qiang Ge, Zhenbiao Zhou, Daniel Creedon, Yi Yang, Michael J. Brear, Deepak Saini, Joseph D. Berry, Mohsen Talei, Richard D. Sandberg, Melissa Kozul, published by KIT Scientific Publishing
This work is licensed under the Creative Commons Attribution 4.0 License.

Volume 3 (2026): Issue 1

Impact of Release Temperature on Hydrogen Jet Mixing with Ambient Air

Figures & Tables

Figure 1

Table 1

Figure 2

Table 2

Table 3

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Table 4

Figure 11

Figure 12

Table 5

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Paradigm

My account